1. Field of the Invention
The present invention relates to a data communication method used for executing data exchange between different networks by connecting a plurality of networks via relay units including gate ways, root hubs, or hubs mutually, and a data communication system using this communication method. More particularly, the present invention relates to a data communication method capable of surely transmitting communication data to a designated node terminal as a destination without a reduction in data transmission capacity per unit time, even when data exchange is executed between the different networks with the intervention of one or more than two networks in communication routes and also data communication routes branch out into plural routes with the travel of communication data, and a data communication system using this communication method.
2. Description of the Prior Art
In the prior art, as disclosed in Patent Application Publication (KOKAI) 59-62245, for example, a data communication system has been widely known in which a plurality of local area networks (referred to as "LAN's" hereinafter) used to execute data exchange between a plurality of stations are connected via gate ways to enable data exchange between LANs.
According to the technology disclosed in the above Publication, in addition to a transmitter/receiver address for designating the transmitter and the receiver of data respectively, both a transmitting or receiving station address indicating the data transmitting or receiving station and a network address indicating the network to which the data transmitting or receiving station belongs have been provided in the transmitter/receiver address of the communication data. Hence, even if data communication is to be carried out beyond its own network, certain data communication between different LAN's has been made possible by referring to these addresses upon data communication.
However, according to the addressing approach used in the above data communication system in the prior art, the network address designated as the destination and the network address peculiar to the LAN in which the communication data reside are compared with each other and then it is determined timely whether or not the communication data reach the destination LAN based on the result that these addresses coincide with each other or not. For this reason, at the time when the data communication is enabled between LAN's with the intervention of one or more than two LAN's in the communication routes, for example, if data communication routes branch out into plural routes with the travel of communication data, it has not been able to be decided which branch route the communication data is to be supplied to, so that the communication data have reached the destination LAN while making a detour on the route. As a result, in the above data communication system in the prior art, such a problem to be overcome has resided that it is difficult to increase data transmission capacity per unit time.
Moreover, according to the addressing approach in the above data communication system in the prior art, such another problem to be overcome has arisen that it is difficult to satisfy the request that the communication data should be broadcasted from one source to plural destinations.